Ballack joined Chelsea from Bayern Munich in 2006

Ballack, 31, has not played since April after undergoing two operations on his left ankle, but he is making progress.

The German said: "I started training last week and December looks good, but I am not setting a specific goal or date when I'd like to play again."

Ballack has already said he will stay at the club in the wake of Avram Grant replacing Jose Mourinho as manager.